AM3270/TR3271 Reference Manual

Glossary
Glossary–4 086705 Tandem Computers Incorporated
IOP. Input output process. Within the context of the 3650/6100 family of controllers,
this type of I/O process is called a CAP (communications access process).
LIM. Line Interface Module. Part of the LIU in a 3650/6100 subsystem, the LIM is the
actual connection to the communication line. It provides the physical and electrical
interface to the outside world.
LIU. Line Interface Unit. A component of the 3650/6100 subsystem. Each LIU
supports a single communications line. There can be up to 15 LIUs in a 6100
subsystem. Each LIU consists of two parts: a Communications Line Interface
Processor (CLIP) and a Line Interface Module (LIM). The LIU is dual-ported to allow
it to communicate through either of the CIUs, providing fault tolerance. (However,
the LIU does not communicate through both CIUs simultaneously.) See also CLIP and
LIM.
message block. Also called a frame. The basic unit of communication for bisync
protocols. Combined message blocks are called “multiblocks.”
multipoint. A data-link configuration in which one station is designated as the
supervisor and controls all communications over the link. This type of link is used to
establish a connection between three or more stations. The other stations are
designated as tributaries.
nonswitched. A line configuration that provides a permanent path between two
stations. This path can be a privately owned cable or a dedicated path leased from a
common carrier. It is generally a leased line.
pad. Also called “padding,” or “PAD characters,” this refers to the bisync convention
of sending leading and/or trailing characters to achieve bit synchronization. This is
different from PAD as it is used in the X.25 protocol, which was developed after
bisync. In X.25, PAD is an acronym for Packet Assembly/Disassembly characters.
path. In the context of the 3650/6100 controllers, the route between a specified CIU
and a CPU. Each CIU has a primary path (Path A) and an alternate path (Path B). The
primary and alternate paths provide fault tolerance if a CIU ever fails. At system
generation, each line of a 3650/6100 family controller must be assigned a primary
path.
point-to-point. A data-link configuration between two stations. This configuration may
exist between a primary and a secondary station or between two combined stations.
pass-through mode. Used by AM3270 access method to connect an AM3270 subdevice
directly to a TR3271 device without an intervening application program. This mode is
typically used to directly attach subdevices controlled by an AM3270 line to an IBM-
compatible host system.
PTP. Pass-Through Protocol. See pass-through mode.
QUO. The protocol used by AM3270 to communicate with Quotron controller
concentrators. The controller concentrator multiplexes the messages that flow from
many Quotron devices through one logical AM3270 subdevice.